Ligand interactions with the solubilized porcine atrial muscarinic receptor.

摘要: Ligand interactions with porcine atrial muscarinic receptor solubilized in a mixed-detergent system (0.4% w/v digitonin and 0.08% cholate) are described. The interacts ligands stereospecific manner, showing about the same affinity for local anesthetics antagonists as was found membrane-bound protein [Schimerlik, M. I., & Searles, R. P. (1980) Biochemistry 19, 3407-3413]. Agonists appear to interact single class of noninteracting sites that correspond low-affinity agonist preparation. Kinetic studies L-[3H]quinuclidinyl benzilate binding indicated two-step mechanism. first step, rapid preequilibrium (K = 5.7 x 10(-9) M), followed by slow conformational change (k1 4 10(-3) s-1; k-1 1.7 10(-4) s-1) receptor-ligand complex. overall dissociation constant calculated from association kinetics (2.3 10(-10) M) agreed well thermodynamic value Kov (2.5 M); however, direct determination K-1 gave 4-fold lower (4.0 10(-5) than predicted. Possible reasons this discrepancy discussed.